When lion consorts go wild

These are some notes on game theory and social behavior in lions. In his book, Evolution and the Theory of Games, John Maynard Smith includes a chapter on asymmetric contests -- games in which two parties begin from different initial conditions. The most vivid example is mating contests between male lions, for which he describes some of the work of Craig Packer and Anne Pusey:

Particular interest attaches to those situations in which two males in the same cooperating group [that is, coalition] fight over possession of females. These fights occur in two situations, which have in common that the asymmetry between owner and non-owner has broken down. The first, and more obvious, case arises when the owner wadners too far from the female, enabling an intruder to come closer to her; ownership is then unclear. The second case arises when two consort pairs come into close proximity. There is then no longer an asymmetry, and a fight may ensue; one male may try to acquire the other's female and thus may come to control two females simultaneously, but in some cases no such attempt is made, and hte fitht seems to result merely form the intolerance felt by an owner of the presence of a second male. This latter case affords a dramatic (because counter-intuitive) example of the importance of asymmetries in settling contests. In thinking about it, it is important to remember that the cost of a contest between male lions is high. Not only is there risk of injury in the contest itself; even an uninjured male would pay a price if its opponent was injured, because a group of males in which some are injured is less likely to be able to defend the female pride against other groups. Because the price is high, dependence on the asymmetry will be strong, and the risk of escalation on the relatively rare occasions when the asymmetry breaks down correspondingly great (Maynard Smith 1982:100-101).

Packer and Pusey (1982) focus their description on the (previously) widely held view that coalition partners "share" mating opportunities:

Because fights over oestrus females are so rarely observed, males of a coalition have been said to 'share' females and to do so becasue they are relatives. However, two factors should be taken into account when attempting to measure differential reproductive success among males of a coalition. First, females in a pride tend to come into oestrus at the same time. In our study, on the first day of 43% of oestrous periods other females in the pride were also in oestrus (n=150). Second, females tend to move to additional mating partners after their first mating partner loses interest in them at the end of oestrus. Subsequent partners show only a brief interest in the female and females seek additional partners most often when their fertility is the lowest. The calculating the relative mating activity of males without controlling for either the number of females in oestrus or the order in which males consorted with a particular female biases against finding any differences in reproductive success (Parker and Pusey 1982:741).

They then discuss the costs of contests between males, and present convention as a likely game theoretic solution:

Costs to males of direct competition for oestrous females can be high: one-to-one fights typical of such encounters often result in wounds to the face and eyes and sometimes in blinding. Even in a gang attack on a single individuals, the lone animal can wound several of its opponents. Furthermore, the loss of a companion through fighting may shorten tenure in the pride. Game theoretical analysis predicts that when costs of fighting are high, contests may be settled 'conventionally' through recognition of asymmetries such as 'owner versus rival' or 'large versus small,' rather than through overt aggression. As differences in size or vigour exist in only about one-third of male coalitions (7 of 20), the 'respect' of ownership in lions is particularly important (Packer and Pusey 1982:741).

References:

Packer C, Pusey AE. 1982. Cooperation and competition within coalitions of male lions: kin selection or game theory? Nature 296:740-742.

Maynard Smith J. 1982. Evolution and the Theory of Games. Cambridge University Press, Cambridge UK.